astronamy

Which of the following statements best describes the general pattern of composition among the four jovian planets?

Jupiter and Saturn are made mostly of hydrogen and helium, while Uranus and Neptune are primarily made of hydrogen compounds such as water (H2O), methane (CH4), and ammonia (NH3)

Look at the densities of the jovian planets. What is the trend?

There is no obvious trend in the densities of the jovian planets.

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Which of the following statements best explains why the densities of Uranus and Neptune are higher than those of Jupiter and Saturn?

They have a higher proportion of hydrogen compounds and rock.

Which of the following best explains why Jupiter’s density is higher than Saturn's?

Jupiter is more massive than Saturn.

Based on the leading scientific theory of solar system formation, which of the following statements best explains why Uranus and Neptune have a significantly different composition and higher density than Jupiter and Saturn?

Jupiter and Saturn captured more gas from the solar nebula than Uranus and Neptune.

What jovian planets are composed mostly of hydrogen and helium?

only jupiter and saturn

what jovian planets have an interior that is mostly liquid or metallic hydrogen?

only jupiter and saturn

what jovian planets have a blue color because of methane

uranus and neptune only

what jovian planets are composed mostly of hydrogen compounds?

uranus and neptune only

what jovian planet has apprx 10 earth -mass core?

all of them

what jovian planets are orbited by rings of ice and rock?

all of them

true or false: only some of the jovian planets have strong atmospheric winds and storms

false; all of them do

what jovian planet has a magnetic field that is stronger than Earths?

all of them

what jovian planet has a solid surface under a thick atmosphere?

none of them

Which lists the jovian planets in order of increasing distance from the Sun?

Jupiter, Saturn, Uranus, Neptune

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Why does Neptune appear blue and Jupiter red?

Methane in Neptune's atmosphere absorbs red light.

Why is Jupiter denser than Saturn?

Its higher mass and gravity compress its interior.

Some jovian planets give off more energy than they receive because of

ongoing contraction or differentiation.

Io experiences tidal heating primarily because __________.

Io's elliptical orbit causes the tidal force on Io to vary as it orbits Jupiter

Io's elliptical orbit is necessary to its tidal heating. This elliptical orbit, in turn, is a result of the orbital resonance among Io, Europa, and Ganymede. This orbital resonance causes Io to have a more elliptical orbit than it would otherwise, because __________.

Io periodically passes Europa and Ganymede in the same orbital position

We cannot see tidal forces or tidal heating; rather, we predict that they must occur based on the orbital characteristics of the moons. What observational evidence confirms that tidal heating is important on Io?

active volcanoes on Io

The orbital resonance also gives Europa an elliptical orbit, so it also experiences tidal heating. However, Europa experiences less tidal heating than Io, because Europa __________ than Io.

is farther from Jupiter

We now know of many Jupiter-size planets around other stars. Suppose that future observations show that one of these planets has two orbiting moons. What additional information, if any, would we need to decide whether these moons experience tidal heating?

We need to know their orbital periods.

What are the characteristics of IO?

-volcanoes currently erupting

-hot, glowing lava visible in some pictures

- source of ionized gas in the donut-shaped charged particle belt around jupiter

what are the characteristics of EUROPA?

ice covered surface with few impact craters

surface features provide evidence of a subsurface liquid ocean

what are the characteristics of GANYMEDE?

heavily cratered terrain adjacent to much younger terrain

largest moon in the solar system

The largest moon in the solar system is _____

Ganymede

THe jovian moon with the most geologically active surface is ____

Io

Strong evidence from both surface features and magnetic field data support the existence of a subsurface ocean on _____

Europa

____ is responsible for the tremendous volcanic activity on Io

Tidal heating

____ is the most distant of Jupiter's four galillean moons

Callisto

The fact that Europa orbits jupiter twice for every one orbit of Ganymede is an example of _____

orbital resistance

Why is Io more volcanically active than our moon?

Io has a different internal heat source.

What is unusual about Triton?

It orbits its planet backward.

Which moon shows evidence of rainfall and erosion by some liquid substance?

Titan

The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their distance from the Sun, from closest to farthest

Earth

Jupiter

Saturn

Uranus

Neptune

The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their size (average equatorial radius), from smallest to largest.

Earth

Neptune

Uranus

Saturn

Jupiter

The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their mass, from lowest to highest

Earth

Uranus

Neptune

Saturn

Jupiter

Saturn’s rings are composed of __________.

lots of individual particles of ice and rock

Saturn’s rings look bright because __________.

light from the Sun reflects off the material in the rings

Which of the following statements correctly describes the motion of the particles in Saturn’s rings?

Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings.

Which of the following is not a general characteristic of the four jovian planets in our solar system?

They are higher in average density than are the terrestrial planets.

Which of the following best describes the internal layering of Jupiter, from the center outward?

The energy in the atmospheres of most of the jovian planets comes ___________,

both the Sun and their interiors, in roughly equal proportions

Which of the following statements comparing the jovian interiors is not thought to be true?

They all have the same exact set of internal layers, those these layers differ in size.

Overall, Jupiter's composition is most like that of ______.

the Sun

Jupiter's colors come in part from its three layers of clouds. Which of the following is not the primary constituent of one of Jupiter's cloud layers?

clouds of sulfuric acid

How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?

They are much faster than hurricane winds on Earth.

What is the Great Red Spot?

a long-lived, high-pressure storm on Jupiter

What atmospheric constituent is responsible for the blue color of Uranus and Neptune?

methane

How does the strength of Jupiter's magnetic field compare to that of Earth's magnetic field?

Jupiter's magnetic field is about 20,000 times as strong as Earth's.

Which of the following statements about the moons of the jovian planets is not true?

Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids.

Which statement about Io is true?

It is the most volcanically active body in our solar system.

Which moon has a thick atmosphere made mostly of nitrogen?

Titan

The Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?

features or erosion, including what appeared to be dry river valleys and lakebeds

Which moon is considered likely to have a deep, subsurface ocean of liquid water?

Europa

Which large jovian moon is thought to have been captured into its present orbit?

Triton

Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?

countless icy particles, ranging in size from dust grains to large boulders

Which statement about planetary rings is not true?

Saturn's rings formed along with its moons 4.6 billion years ago.

The main ingredients of most satellites of the jovian planets are

hydrogen compound ices.

Saturn's rings

are continually supplied by impacts between small moons.

Which of the following gases is not a significant ingredient of the jovian planet atmospheres?

carbon dioxide

Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?

They actually contain relatively little material in a gaseous state.

According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?

Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula

Which of the following most likely explains why Jupiter's interior releases so much heat?

Jupiter is contracting very gradually.

What would happen to Jupiter if we could somehow double its mass?

Its density would increase but its diameter would barely change.

Which planet may have helium rain in its interior, and what does this rain do?

Saturn, where it generates heat as it falls downward.

Why does Jupiter have three distinct layers of clouds?

The three layers represent clouds made of gases that condense at different temperatures

Which of the following best why we see horizontal "stripes" in photographs of Jupiter and Saturn?

The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.

Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?

Temperatures on Jupiter and Saturn are too high for methane to condense.

Which jovian planet should have the most extreme seasonal changes?

Uranus

Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?

The region is full of gases that become ionized after they are released from volcanoes on Io.

Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?

Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.

All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io?

Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites.

Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?

Astronomers have detected small lakes of liquid water on Europa's surface.

Which of the following is most unlikely to be found on Titan?

lakes of liquid water in the warmer equatorial regions

Why do astronomers believe that Triton is a captured moon?

Triton orbits Neptune in a direction opposite that of Neptune's rotation.

Which statement about Saturn's rings is not true?

The rings must look much the same today as they did shortly after Saturn formed.

If the star Alpha Centauri were moved to a distance 10 times farther than it is now, its parallax angle would

get smaller

What do we need to measure in order to determine a star's luminosity?

apparent brightness and distance

What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?

the time between eclipses and the average distance between the stars

Which of these stars has the coolest surface temperature?

a K star

Which of these stars is the most massive?

Which of these stars is the most massive?a main-sequence A star

Which of these stars has the largest radius?

a supergiant star

Which of these stars has the longest lifetime?

a main-sequence M star

The total amount of power (in watts, for example) that a star radiates into space is called its _________

luminosity

For example, the luminosity of the Sun is 3.8 x 1026 watts.

According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?

Its apparent brightness will decrease by a factor of 9

The inverse square law for light tells us that the light gets dimmer with increasing distance by the square of the distance, so tripling the distance decreases the brightness by a factor of 32 = 9.

Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?

Calculate the star's luminosity if we know its distance, or calculate its distance if we know its luminosity.

If star A is closer to us than star B, then Star A's parallax angle is _________.

larger than that of Star B

A larger parallax angle means the star is closer.

Ten parsecs is about _________.

32.6 light-years

You find this by remembering that 1 parsec = 3.26 light-years.

Star A has an apparent magnitude of 3 and star B has an apparent magnitude of 5. Which star is brighter in our sky?

Star A

The magnitude scale is "backward" so that smaller numbers mean greater apparent brightness.

From hottest to coolest, the order of the spectral types of stars is _________.

OBAFGKM

Our Sun is a star of spectral type _________.

G

Because the spectral sequence is OBAFGKM, the Sun's spectral type of G means that the Sun's surface is hotter than that of K and M stars, but cooler than that of O, B, A, and F stars.

Astronomers can measure a star's mass in only certain cases. Which one of the following cases might allow astronomers to measure a star's mass?

The star is a member of a binary star system.

If we can measure the orbital properties of the star around its companion, then we can measure the mass with Newton's version of Kepler's third law.

Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?

spectroscopic binary

We measure Doppler shifts by looking for shifts in the wavelengths of spectral lines.

The axes on a Hertzsprung-Russell (H-R) diagram represent _________.

luminosity and surface temperature

We plot luminosity on the vertical axis and surface temperature (or spectral type) on the horizontal axis.

What can we infer, at least roughly, from a star's luminosity class?

its size (radius)

The major luminosity classes run from I for supergiants to V for main sequence stars.

On an H-R diagram, stellar radii _________.

increase diagonally from the lower left to the upper right

Small radius white dwarfs are down near the lower left, while large radius supergiants are in the upper right .

On an H-R diagram, stellar masses _________.

can be determined for main sequence stars but not for other types of stars

Along the main sequence, mass decreases from upper left to lower right; but there is no clear pattern to masses for stars that are not on the main sequence.

How is the lifetime of a star related to its mass?

More massive stars live much shorter lives than less massive stars.

This is true massive stars burn through their nuclear fuel at a much greater rate than less massive stars.

Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?

Spectral type M2, luminosity class I

Spectral type M means the star is cool and red, and luminosity class I means it is a supergiant.

What is the common trait of all main sequence stars?

They generate energy through hydrogen fusion in their core.

A star becomes a main-sequence star when it first starts fusing hydrogen into helium, and it ends its main-sequence life when it exhausts its central core supply of hydrogen for fusion.

Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?

Earth would be inside the supergiant.

This is true because a supergiant's radius is typically much more than 1 AU.

What is a white dwarf?

the remains of a star that ran out of fuel for nuclear fusion

Once the nuclear fuel runs out, the star can no longer shine; for relatively low-mass stars, gravity then compresses its remaining core into a white dwarf.

All stars are born with the same basic composition, yet stars can look quite different from one another. Which two factors primarily determine the characteristics of a star?

its mass and its stage of life

Mass determines the star's life progression, so the star's current place along that progression depends on its current stage of life

Based on the definition of apparent brightness, which units are appropriate for its measurement?

watts per square meter

Apparent brightness is defined as the power of starlight reaching us per unit area. Power has units of watts and area has units of square meters.

Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore:

Both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A.

Luminosity is an intrinsic property, so two identical stars will always have the same luminosity. But apparent brightness follows an inverse square law with distance, so the fact that Star A is twice as far away makes it 22 = 4 times dimmer.

Which of the following statements about spectral types of stars is not generally true?

The spectral type of a star can be used to determine its distance.

Spectral type tells us surface temperature, but to calculate the star's distance we need to know its luminosity and apparent brightness (and then use the inverse square law for light).

Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?

Rigel has a higher surface temperature than Sirius.

This is true because the spectral sequence from hot to cool is OBAFGKM, which means spectral type B is hotter than spectral type A.

To calculate the masses of stars in a binary system, we must measure their _________.

orbital period and average orbital distance

We can then apply Newton's version of Kepler's third law to find the sum of their masses.

Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The most likely explanation is that _________.

the star is a member of an eclipsing binary star system

The dimming comes during periodic eclipses

You observe a star and you want to plot it on an H-R diagram. You will need to measure all of the following, except the star's _________.

mass

You do not need to know mass to plot a star on the H-R diagram.

The approximate main-sequence lifetime of a star of spectral type O is _________.

3 million years

O stars are the shortest-lived of all stars, because they are the most massive and therefore the most luminous.

How did astronomers discover the relationship between spectral type and mass for main sequence stars?

By measuring the masses and spectral types of main-sequence stars in binary systems

We can only measure mass directly for stars in binary systems, so this is how the relationship was first discovered.

The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?

The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.

Only O stars have died, so the cluster is no more than a few million years old

The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is most likely to be located in the halo of our galaxy?

The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.

This is an old cluster so it must be a globular cluster, and most globular clusters are in the halo of the galaxy.

Which of these stars has the greatest surface temperature?

a 30 m sun main-sequence star

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